Apparatus for aeration without significant agitation to deplete and biodegrade sludge

ABSTRACT

An improved method and apparatus for aeration of septic tanks and the like. Because of the interrelationship of the rotating impeller, an air plate and the horsepower of the unit in comparison with the volumetric size of the sludge tank, the unit disperses extremely small reduced pressure microbubbles adjacent the area of the impeller. These reduced pressure microbubbles are thereafter dispersed throughout the wastewater by Brownian movement without agitating the sludge. As a result, there is substantially increased lateral oxygen transfer to replace the oxygen used by the aerobic bacteria. The sludge is therefore efficiently digested without the need for huge, expensive and energy inefficient equipment.

FIELD OF THE INVENTION

This invention relates to vacuum aeration units with improvedconstruction and methodology in comparison with those of our earlierU.S. Pat. No. 5,951,867 issued Sep. 14, 1999.

BACKGROUND OF THE INVENTION

As explained in our earlier-above referenced U.S. Patent, there is acontinuing need for the development of improved bacterial breakdown ofsewage waste material. This invention relates to an improvement on ourearlier patented device. It allows for enhancing the lateral oxygentransfer to allow aerobic bacterial to sufficiently and efficientlydecompose waste material, often without objectionable odors.

Prior devices, including the device of our earlier U.S. Pat. No.5,951,867 depended upon substantial agitation of all of the sludgematerials in tanks to enhance the rate and efficiency of aerobicbacterial decomposition. As a result, large horsepower units and energyexpenditures were often required in order to achieve sufficientagitation to enhance lateral oxygen transfer.

In accordance with the improvement of the present invention, a unit hasbeen developed which is not dependant upon high horsepower and highenergy consumption. This goal has been achieved by understanding therelationship between the configuration of the air plate of the unit, theimpeller design and the horsepower in relation to the ratio of volume inthe tank.

Accordingly, it is a primary objective of the present invention toprovide a sewage aeration unit which is low in energy consumption, whichhas a high degree of lateral oxygen transfer to replace the oxygen usedby the aerobic bacteria during the digestion process, and which enhancesthe production of reduced pressure microbubbles capable of dispersingthemselves throughout the wastewater in the septic tank by Brownianmovements, all without agitating the sludge in the tank.

The method and means of accomplishing the above objectives andadvantages as well as others will become apparent from the detaileddescription of the invention which follows hereinafter.

SUMMARY OF THE INVENTION

An improved method and apparatus for aeration of septic tanks and thelike. Because of the interrelationship of the rotating impeller, an airplate and the horsepower of the unit in comparison with the volumetricsize of the wastewater tank, the unit disperses extremely small reducedpressure microbubbles adjacent to the impeller area. These reducedpressure microbubbles are thereafter dispersed throughout the wastewaterby Brownian movement without agitating the sludge. As a result, there issubstantially increased lateral oxygen transfer to replace the oxygenused by the aerobic bacteria. The sludge is therefore efficientlydigested without the need for huge, expensive and energy inefficientequipment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the aeration device of the presentinvention.

FIG. 2 is an exploded view of the aeration device of FIG. 1.

FIG. 2A is a front view of the aeration device.

FIG. 3 is a bottom view of the aeration device of the present invention.

FIG. 4 is a top view of the aeration device of the present invention.

FIG. 5 shows a plan view of the construction of the air plate.

FIG. 5A shows a side view of the air plate.

FIG. 6 is a side view of the impeller showing the angles of the bladewith respect to a horizontal plane.

FIGS. 7 & 8 show schematically the microbubbles and the agitationgenerated in the surrounding area adjacent the impeller.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The unit, best illustrated in overall perspective in FIG. 1, is a devicewhich may be fitted in a conventional septic tank. The aeration device10 is operated by motor 12, energized via electrical hookup 14. As seenin FIG. 2, the unit 10 has air intake lines, 16 and 18, which drawambient air. Motor 12 is mounted to motor mount plate 20 which isattached to circular housing wall 22. Mounted inside of circular housingwall 22, and attached to motor 12 is drive shaft 24. Mounted to circularhousing 22, opposite motor 12 is air plate 26. Below air plate 26 andspaced apart therefrom, is impeller 28. Impeller 28 is held adjacent tothe air plate 26 by a hex nut 30 attached to the end of drive shaft 24as best illustrated in FIG. 3. Air intake tubes 32 and 34 are shown,adjacent the side wall of housing 22.

The configuration of air plate 26 is best illustrated in FIG. 5 whichdepicts a plan view of the unit. As seen in FIG. 5, air plate 26 has aseries of generally parallel concentrically positioned apertures 35 witha plurality of curved or arcuate slots 36 crossing the concentric ringsin a manner that matingly matches the shape of the trailing edge of theimpeller 28. Air plate 26 is preferably made of a polymeric plasticmaterial such as an alpha olefin polymer. The air plate 26configuration, together with the concentrically positioned rings of airholes 35 and the arcuate air slot 36 enhance the preparation of vacuummicrobubbles in the liquid adjacent impeller 28.

The impeller 28 is configured of four distinct blades, 38, 40, 42, and44 (FIG. 3). Each blade has an arcuate short trailing edge 46 and alonger forward edge such as at 48. Looking at the blade as illustratedin FIG. 6, it does not dwell in a single horizontal plane but rather inmoving from trailing edge 46 it curves up and away from the horizontalplane as one moves from trailing edge 46 to forward edge 48. The bladerotates as indicated by directional arrow 50 (looking up from thebottom). As impeller 28 rotates in the direction indicated by arrow 50,air is pulled through the concentrically positioned apertures in themanner illustrated in FIG. 7. In particular, air is pushed through airintakes 16 since the atmospheric pressure is greater than the partialvacuum created, and also through air tubes 32 and 34 through air plate26 as impeller 28 rotates in the manner shown by directional arrow 50,air above air plate 26 goes through the concentrically positioned rings.Vortexes 52 are constantly being disrupted by larger volumes of airpushed through slots 36 which disrupt the air bubbles tending to makethem even smaller. The smaller bubbles then transfer down into the wateradjacent and around the area of the impeller as illustrated in FIG. 7.Because the bubbles are so small (sized generally of 100 microns to 500microns) and are also low pressure air bubbles, they move like colloidalparticles via Brownian movement throughout the wastewater tank toenhance lateral oxygen transfer. In this way, the invention results areachieved.

It has been found important there be a proper horsepower ratio withrespect to the volume of unit. For example, one does not want to agitateor disturb all of the sludge/liquid in the septic tank. If you do this,it requires too much energy and the amount of oxygen transfer to thebacteria is decreased. Correspondingly, if only the vacuum air bubblesare moving via Brownian movement, the chances of interaction with waterfor dissolved oxygen transfer are substantially increased therebyincreasing transfer of oxygen to bacteria. Generally speaking, the ratioof the volume of the tank to horsepower should be 5000 gallons or lessper horsepower to move or mix. If more than 5000 gallons of water perhorsepower, it will not move the water. In actual operation, the unitfor example can operate at about 3,000 rpm. The forward edge of theimpeller blade 28 when it crosses the slot creates the whirlpool effectand the angle of pitch above the horizontal plane from the trailing edge46 to the forward edge 48 of the blade is about 6°. Ideally the unitshould operate at from six inches to twelve inches below the watersurface in the tank.

While not wishing to be bound by theory, it is believed the unit worksas follows. Bacterial cell respiration produces the energy for growthand division. This energy is supplied by what we call wet combustion,the oxidation of organic chemical compounds broken down by the bacteriain the presence of dissolved oxygen.

Bacterial growth and multiplication must take place in a aqueous mediumpossessing carbon and nitrogen compounds in a form capable of beingassimilated to provide energy for the cells respiration process.Nutrient ingestion by bacteria must take place through a cell wall andmembrane which require minute particles of molecular size dispersed insolution for ready transport.

These conditions are met here in an aqueous medium with minimal or nomixing so that oxygen, food, and bacteria have the most effectiveinterface for assimilation and digestion.

The prime mover of the water (impeller 28) moves the water out of theair chamber which will cause the air to enter, and when the watercompletely evacuates the space above the air plate 26, the air is pushedinto the space (air tube), through the holes provided in the air plate.The water below the impeller replaces or fills the space above theimpeller. As the air above the air plate is pushed down into therecirculating water from below, the air streams from the several airholes in the plate make empty cylinder in the water or vortexes(vortices) which are periodically cut or terminated and reformed by theblades of the impeller. Thus, forming smaller and smallest voids in thewater leaving the end of the air chamber. The water space formed, at auniform time and distance, have a volume with air at a lower pressurethan the water. Therefore, the volume will reduce, until the air iscompressed. The size of the bubble will be smaller than the diameter ofthe vortex that was formed at the air plate. The air plate thereforesets the size of the bubble that forms.

What is claimed is:
 1. An apparatus for aeration of septic tankwastewater comprising: a motive power means; an impeller operativelyconnected to the motive power means; an air plate positioned betweensaid motive power means and said impeller; said air plate having aseries of concentrically positioned apertures, periodically interruptedwith crossing arcuate air slots, wherein the concave side of the arcuateair slots faces in the direction of roatation of the impeller.
 2. Theapparatus of claim 1, wherein the impeller has a plurality of blades,having a forward edge and a pitched upwardly inclined trailing edge.